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Table of Contents
CASE REPORT
Year : 2020  |  Volume : 52  |  Issue : 3  |  Page : 101-103

Novel orthotic design for lateral band attenuation of finger proximal interphalangeal joint


Occupational Therapist, Certified Hand Therapist (OTR, CHT), Hands-On-Care, San Jose, California, USA

Date of Submission08-Aug-2020
Date of Acceptance21-Sep-2020
Date of Web Publication23-Oct-2020

Correspondence Address:
Saba Kamal
499 Blossom Hill Road, San Jose, CA 95123
USA
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijoth.ijoth_30_20

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  Abstract 


Patients with lateral band attenuation present with a snapping finger which may be misdiagnosed for a trigger finger. Lateral bands work as a flexor after 30° flexion of the proximal interphalangeal (PIP) joint, assisting with flexion of the PIP joint. It assists central slip and works as an extensor from 30° onward, extending the PIP and distal interphalangeal joints. Loss of coordination between the multiple, specialized components of the extensor mechanism results in tendon imbalances, leading to altered interphalangeal joint flexion and extension forces. This case report is to introduce the fabrication of an orthotic to tackle finger injury for quick and effective conservative treatment. The indications and functions of the orthosis are discussed. The fabrication process is illustrated, including materials needed and steps of molding the splint. Wearing regimen and precautions are highlighted to ensure effective patient compliance to the orthosis program for finger injury. Objective data collected include pre- and post-pain level and outcome measures indicative of improved functional performance.

Keywords: Lateral Band Attenuation, Snapping Finger, Splint


How to cite this article:
Kamal S. Novel orthotic design for lateral band attenuation of finger proximal interphalangeal joint. Indian J Occup Ther 2020;52:101-3

How to cite this URL:
Kamal S. Novel orthotic design for lateral band attenuation of finger proximal interphalangeal joint. Indian J Occup Ther [serial online] 2020 [cited 2020 Nov 24];52:101-3. Available from: http://www.ijotonweb.org/text.asp?2020/52/3/101/298983




  Introduction: What is Lateral Band Attenuation? Top


Lateral bands pass on either side of the proximal phalanx and stretch all the way to the distal phalanx.[1] Their function is to retain and position the common extensor mechanism during proximal interphalangeal (PIP) and distal interphalangeal (DIP) joint flexion.[1]

Lateral bands work as a flexor after 30° flexion of the PIP joint, assisting with flexion of the PIP joint. They assist central slip and work as an extensor from 30° onward, extending the PIP and DIP joints.

Loss of coordination between the multiple, specialized components of the extensor mechanism results in tendon imbalances, leading to altered interphalangeal joint flexion and extension forces.[2] Patients usually present with finger snapping at the PIP joint, after flexion is initiated at DIP. Then, the finger snaps into flexion [Figure 1].
Figure 1: Finger Stuck in Extension

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A differential diagnosis must always be performed to rule out trigger finger. Assessment for annular pulley (A1) tenderness must be performed and if present then one cannot rule out trigger finger,[1] and must suspect attenuation of the lateral bands. Case history may indicate trauma or even diagnosis such as Parkinson's or Ehlers–Danlos syndrome. In a lateral band involvement, the functional limitation is of the finger stuck in extension compared to trigger finger where the finger is stuck in flexion.

Treatment

When PIP joint is kept in 30° flexion, the finger does not lock with flexion and extension movements.[3]


  Purpose of the Orthosis Top


Full extension can cause the lateral band to lock and snap as the finger moves from full extension to flexion.

Designing a lateral band attenuation orthosis to keep PIP joint in 30° flexion, allowing full flexion and −30° extension. The reason behind −30° extension is to advance the lateral bands below the PIP joint axis, to make them work as a flexor.

Materials Needed for Novel Splint, See [Figure 2]
Figure 2: Splinting Material Needed for the Novel Orthotic Design

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  • Two pieces of low-temperature thermoplastic material from 3/32 Tailorsplint™ material
  • Nail polish
  • Self-bonding solvent.


Fabrication Steps

  • Cut the first piece of the strip, 3/32” width of the thermoplastic material, approximately 5” in length, to wrap around the PIP joint of the finger
  • Cut the second piece of the thermoplastic material 3/32” in width and ¾” in length
  • Use the bonding solvent to remove the coat from the ends of the 5” Tailor thermoplastic strip to allow for adherence of the ends
  • The bonding solvent should be applied to the entire piece of the ¾” strip.


When designing a novel orthotic for lateral band attenuation of finger PIP joint, the thermoplastic material must cross in the middle on the volar aspect of the PIP joint. The finger must be kept in slightly more than 30° flexion, to account for stretch. The second piece is then used to wrap around the intersection on the volar aspect to secure it and to set the angle that is needed for the finger, to prevent it from snapping, which typically is at − 30° extension. This is done by pinching it and flaring the loops further away from the PIP joint to allow for the flexion. The further the loops are away from the joint, the more the negative angle at the PIP joint.

The nail paint is used at one end to remind the patient which way to wear the splint.


  Case Report Top


We describe the case of a patient who presented to the clinic with a diagnosis of trigger finger in the right small finger and a new diagnosis of Parkinson's disease. The patient complained that the finger would snap when she tried to bend it in flexion and never locked in flexion. It would just snap back and forth with movement, making it difficult to perform functional activities. On assessment, no tenderness was noted at A1, and the locking was in extension rather than flexion. When the finger was kept in 30° flexion and the patient was asked to move the finger, it did not snap, but the moment full extension was allowed, the finger got stuck and then snapped with flexion. The lack of tenderness at the A1 pulley, locking in extension rather than flexion, led the therapist to the diagnosis of lateral band attenuation [Video 1].

The clinician provided the patient with a novel orthotic design for lateral band attenuation of the PIP joint of the finger. However, the clinician found that if the loops were too close to the PIP joint, it failed to correct the snapping in the finger as it allowed for too much extension. To keep the loops as far apart as possible to allow for more flexion, the clinician used a strip and wrapped it around the intersection of the orthosis loop on the volar side. This kept the loops apart and maintained the needed 30° flexion.

The clinician then used a nail polish on the proximal end of the splint for the patient to distinguish between the two ends [Figure 3]. The results are shown in Video 2.
Figure 3: Patient Able to Bend the Finger Without Locking

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Wearing Time

During all waking hours (functional splint), patients can remove it at night, if they choose to do so.

Contraindications

None. Patients did not develop contractures at the PIP joint partly because these patients seem to be prone to laxity of the joints. However, further research is indicated to determine the long-term effects of the splint wear and development of contracture in other types of injuries.

Supplemental Data



Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial Support and Sponsorship

Nil.

Conflicts of Interest

There are no conflicts of interest.



 
  References Top

1.
Lim R, Sreedharan S. Lateral band subluxation: An unusual case of pseudotrigger. J Hand Microsurg 2015;7:208-211.  Back to cited text no. 1
    
2.
Elzinga K, Chung KC. Managing swan neck and boutonniere deformities. Clin Plast Surg 2019;46:329-337.  Back to cited text no. 2
    
3.
Fox PM, Chang J. Treating the proximal interphalangeal joint in swan neck and boutonniere deformities. Hand Clin 2018;34:167-176.  Back to cited text no. 3
    


    Figures

  [Figure 1], [Figure 2], [Figure 3]



 

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